1. Field of the Invention
The invention relates to a method for the measurement of the total content of organic carbon and of nitrogen in water, where a sample, taken from the water to be investigated and analyzed, is evaporated, wherein the organic carbon is oxidized to carbon dioxide, wherein the nitrogen is oxidized to nitrogen oxide in a thermal reactor, and wherein the measurement is performed based on the gas sample, formed from the sample containing carbon dioxide CO.sub.2 and nitrogen oxide NO.
2. Brief Description of the Background of the Invention Including Prior Art
The following abbreviations will be used in the following:
TOC=total organic carbon, indicating the total carbon present in the water to be measured in the form of organic compounds.
TIC=total inorganic carbon, indicating the total carbon in the form of inorganic compounds present in the water to be measured.
TC=total carbon, indicating the total carbon present in the water to be measured.
The organic part of carbon of the total organic carbon (TOC), is an oxygen consuming user and thus of interest in the determination of the chemical composition of waters. The German Industrial Standard 38 409 (H) provides a basis for the determination of the total organic carbon (TOC) value.
The German Industrial Standard 38,409 (H) corresponds to the proposed International Standard ISO/DS 8245, submitted on Jan. 16, 1986 and defines the designations TC=total carbon, TIC=total inorganic carbon and TOC=total organic carbon.
TN=total nitrogen, indicating the total amount of nitrogen present in the water to be measured. The designation TN is defined in the proposed German Industrial Standard DIN 38,409, part 27.
Frequently, only a part, i.e., the part of the dissolved total organic carbon (TOC) is captured in practical situations instead of the correct values. Frequently, also volatile organic components can be present in water, which are lost during the separation of the sample of inorganic compounds. Thus, the total organic carbon (TOC) value, is not completely captured with such a method.
The part of bonded nitrogen, total nitrogen (TN), is of interest in addition to the total organic carbon (TOC) value. The total nitrogen (TN) value gives an indication relative to the load of the water with nitrogen compounds derived from natural and industrial discharges. A proposal for the measurement of the total nitrogen (TN) is given in the proposed German Industrial Standard 38 409, part 27.
Total organic carbon (TOC) determinations are known. The total carbon (TC) and the total inorganic carbon (TIC) are measured and the total organic carbon (TOC) is determined by difference formation, compare for example German Printed Patent documents DE-OS 2,811,135 (equivalent U.S. Pat. No. 4,217,108), DE-OS 2,458,143 (equivalent U.S. Pat. No. 3,854,881), DE-OS 2,322,293 (equivalent U.S. Pat. No. 3,814,583), and European Patent document EP-PS 0,150,923 (equivalent U.S. Pat. Nos. 4,626,413, 4,666,860, 5,047,212).
A method for the continuous and quantitative determination of organic and inorganic carbon compounds in water is taught in the German Printed Patent document DE-OS 3,909,240, wherein the water to be analyzed is acidified in a degasification vessel. A transport gas flow is fed through the water into the degasification vessel. Water and transport gas pass from the degasification vessel into a decomposition reactor. The carbon dioxide CO.sub.2 content of the transport gas is determined downstream of the degasification container or downstream of the decomposition reactor. The parts of organic and inorganic carbon compounds are separated from each other or are determined as a sum.
F. Ehrenberger teaches in the paper entitled "For the determination of the oxygen requirement values and carbon characterizing values in the water quality determination", GIT Fachz. Lab. 23, Volume 8/79, pages 738 through 747, several methods for the determination of total organic carbon (TOC), where the methods are based on wet chemical or thermal reaction of the organic content materials and on the quantitative oxidation of the organically bonded carbon to carbon dioxide. The carbon dioxide CO.sub.2 content is determined by a chemical or physical method. A simultaneous determination of nitrogen is not provided for in the methods described by F. Ehrenberger.
A value obtained by a total nitrogen (TN) auxiliary measurement is added in individual cases to a value of a total organic carbon (TOC) measurement by furnishing of a corresponding analyzer as set forth in the German Printed Patent Document DE-OS 2,621,616 and in the equivalent U.S. Pat. No. 4,066,402. This method is expensive and generates undesirable delay times of the display. Frequently, the calibration is performed manually with a high-purity zero-conductivity water for the zero point establishment and with a calibration solution for establishing the sensitivity. In addition, measurement errors caused by the principle of the method are accepted. Thus, deviations from the predetermined sensitivity occur if a base load of carbon dioxide CO.sub.2 becomes changed.
The German Printed Patent document DE-OS 2,621,616 to Yoshiki Komiyama teaches an analytical method and device for the determination of the total nitrogen and/or carbon contents in aqueous solutions which contain nitrogen and/or carbon containing material.
The German Printed Patent document DE-OS 3,937,141 to Walter Fabinski, having an equivalent U.S. Pat. No. 5,055,688. teaches a non-dispersive infrared gas analyzer for the simultaneous measurement of the concentration of several components of a gas sample. The NDIR gas analyzer is suitable for the determination of the two gas components, carbon dioxide and nitrogen oxide. An analyzer is connected to and receives signals from the receiver detectors. A control and display unit is connected to the analyzer.
The reference M. Ascherfeld et al. in "Technisches Messen - tm", Volume 57/1990, Issue 1, pages 11-17, teaches "Expanded Possibilities and Applications with the NDIR Photometer Uras 10E".
The German Patent 2,105,307 to Theodor Bilichnianski teaches a liquid dispenser for feeding of reagents to an automatically operating apparatus for the continuous analysis of samples.
The German Patent DE-3,640,718 C2 to Willi Apel et al. teaches a membrane capacitor for measuring of very small pneumatic alternating pressures.
The German Printed Patent document DE-OS 3,909,240 Al to Hans Duve teaches a method for the determination of disintegratable carbon compounds in water.